Conventionally water cooling channels of grids (plate of Oxygen Free Copper) are connected with external hydraulic circuit (stub of stainless steel) by using a solid state welding process, known as friction welding (FW). The joining in this technique is realized by generating heat through mechanical friction between the joinable plate and stub while they are in relative motion. Further, an axial force is applied to plastically displace and fuse the material with each other.
An important aspect of manufacturing of actively cooled accelerator grids for example (180 mm width, 500 mm height and 10 mm thickness) for Neutral Beam (NB) sources is the interfacing of the copper (Cu) water cooling stub with Cu base plate. Conventional procedures utilize a process of friction welding where joining is achieved by the heat of friction and addition of pressure. Limitations related to process like the restricted choice of orientation, vibration during the process, the basic plate accuracies achieved before welding, need of post welding machining, formation of intermetallic compound between SS and Cu, lack of full inspectability and no options for repairing the welding joint has led to a need for identifying a joining configuration and process which overcomes the drawbacks of the existing one followed by qualification of the same.
Prior art techniques of FSW include the following drawbacks: (a) the required relative motion between pipe and plate limits the welding positions and orientation; (b) vibration during the welding process damages the already achieved dimensional accuracies of the grid plate which is undesirable (specifically in the case of angled grid); (c) need for removal of excess material accumulation on the outer surface of the joining which leads to a post-welding finishing machining stage in the manufacturing process; (d) the metallurgical incompatibility of SS and Copper during the FW forms undesirable intermetallic compound; (e) an effective inspection methodology for this kind of joints have not been established and therefore the full integrity of the weld joint cannot be guaranteed; and (f) in case of any unacceptable defect found in the joint, there are limited options available for repairing the weld and therefore large numbers of plates have to be wasted.
It is therefore an object of the invention to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which achieves full weld penetration.
Another object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which allows 100% volumetric inspection to detect defects.
Yet another object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which avoids grid rotation and maintains already achieved dimensional accuracy.
A further object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which eliminates the use of filler material.
A still further object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which requires zero post-welding finishing machining.
Another object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which produces metallurgically consistent weld and avoid formation of intermetallic compounds.
A still another object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which employs a fully automatic welding technique.
Yet another object of the invention is to propose an improved method of manufacturing actively cooled accelerator grid with full penetration weld configuration, which produces repeatable, repairable and consistent weld joint.